Pulp manufacture



Patented Nov. 1, 1932 UNITED s'rirnis ROGER W. RICHARDSON, OF WILMINGTON,

DELAWARE, 'hss'renon 'ro E. I. Du roar nn NEMOUBS & COMPANY, OF WILMINGTON, DELAWARE, A OORPORATION OF DELAWARE ruLr MANUFACTURE E't'o Drawing.

This invention relates to the manufacture of paper pulp and has for an object the more eflicient and economical manufacture of a superior grade of pulp, suitable for use in the paper, nitrocellulose, andkother industries by the processing of wood and other vegetable fibrous materials.

. It is a further object of the invention to provide an improved process .for the manufacture of cellulose pulp from highly resinous wood. 7

These and other objects and advantages of the invention, which will more fully hereinafter appear are attained by preliminarily treating the fibrous material with a'naqueous solution of ammonia followed by digestion with an ammoniumbisulfite solution.

'Accordingto this invention I am able to secure a high grade of pulp from a variety of raw cellulosic materials including those woods high in resin content, such as, for example, jack pine, pitch pine, scrub pine Douglas fir, etc., whichhave been difficult, i not impossible, to process by theordinary sulphite method. Because of the milder action achieved according to my invention by a preliminary treatment with an ammonia; cal solution for the extraction of resinous, gummy, and other cemen titious and binding material, followed by ammonium bisulfite cooking, to complete the defibering of the'cellulose, economies in the usual bleaching operation are possible as well as the production of a light colored pulp of better than ordinary quality and relatively free from degraded cellulose. Furthermore, due to the milder loosening and defibering action of the chemicals employed according to my invention, a higher yield of pure cellulose is obtained. The high. strength of the pulp fibers renders them particularly valuable for paper manufacture and like uses. 4

Although the use of Wood in the form of chips is more specifically described in the following description of operating conditions, it will be understood that the references thereto are simply by way of illustration and the invention should be construed as broadly applicable to cellulosic materials of any form or variety. Furthermore, the specific condi- Application filed October 21, 1931. Serial no. 570,2555.

tions of operationiemployed, includin for instance, the temperature and length 0% preliminary treatment with ammoniacal solutions, the temperature and length of cook with ammonium bisulfite, and the strength of the solutions or liquors, may be varied depending upon the particular raw material under treatment and the desired quality of the final product.

It is well known that under ordinary sulfite pulping conditions the fiber is seriously degraded at the inception of the chemical operation due to the fact that the acid radical of the sulfite cooking liquor penetrates the chips more rapidly than does the basic ion of the chemical. This basic ion isnecessary, however, to prevent excessive hydrolysis and dc radation of the cellulose.

, t is possible, according to m invention,-

after the chips have been subjected to regcster, difi'used therein thruout the chips,

fee

liminary extraction, by washing the c ips tt with a weak solution of aqua aonia and -leaving a portion of the washing solution in the digester. The ammonium blsulfite solution (with or without sulfurous acid solution, depending upon the amount of ammonia in the washwater left in the digester) is thereafter introduced into the digester and ammonium bisulfite formed therein. In this Way the base is difiused thruout the chips before digestion and as the acid subsequently penetrates, when introduced for purposes of digestion, it is neutralized in part by the dif fused base and as a consequence no excessive a nor harmful degradation of the cellulosic constituents occurs.

It is also possible by carrying out the process as outlined above to shorten the ordinarily long penetration period of the usual sulfite cooking, because there is quickly formed thruout the body. of the chips a solution of sulphite acid containing ammonium salt, and temperatures which would usually be excessive at this eriodof the digestion are not harmful to t e fiber.

In certain cases, such as in pulping resin one woods 1particularly dilficult to digpst, as, for examp e, the heart wood of slas pine, highly resinous yellow pine, etc., it may not be desirable to carry out the process in the specific manner heretofore indicated. In such a case the ammonia may be thoroughly washed out of the chips after the preliminar treatment and (if the washing is not thoroug the residual ammonia does no harm and serves as part of the base content of the acid) ammonium bisulfite liquor introduced into the digester and the cooking carried out in the usual manner save that a shorter penetration nary extraction.

' period and milder cooking treatment are poswoods for ordinary sulfite pulping;.but by.

combining the advantageous effects of the preliminary ammonium hydroxide extraction treatment and the extraordinary solving action of ammonium bisulfite cook liquor for these resinous and gummy materials a higher grade pulp can be produced than is usual by ordinary methods.

The extracting operations above referred 'to are carried on by vigorously circulat ng a dilute ammonium hydroxide solution over the chips to be treated for a period of from 30 minutes to 3hours and at a temperature of from about 90180 C. although. the preferable temperature range is 100-110 C.

- .After the extraction operation the ammonium hydroxide liquor is partly or wholliy removed from thechips, as hereinbefore escribed, while at a temperature of from about (SO-80 O. and the chips 'are washed with water or dilute ammonia withinthe same temperature range, i. e. GO-80 C.

Although the details and methods of car-.

\ rying. out the invention may be varied within wide limits without departing from the invention or sacrificing any of the advantages thereof,- the following examples will serve to indicate the preferred embodiments and methods of vention.

Ewample 1.-Into a digester of conventional design and of suflicient strength to withstand t e conditions oftem erature and ressure encountered in the u ping of woo and "equipped with a suitab e pump for circulation of extraction liquor, there are introdueed 100 parts by weight of hemlock chips.

Thereafter 500 parts 0 ammonium hydroxprocedure for executing the in-.

ide of 2.5% stren h are introduced and circulated through t e chips for a period of minutes at a temperature of 110 0. Following the circulation the materials in the digester are allowed to cool to a temperature of C. when the ammonium hydroxide so-- lution is drained ofi. without release of pressure. The ammonia is recovered from the extraction liquor by distillation or other suitable means and the extracted material recovered if desired.

Two hundred parts of a 1% NH OH so-' lution are then introduced into the digester and circulated th'ru the chips at 70 b. for about 15 minutes. The ammonia solution is drained ofi except for (35 parts which are left i1111 the digester in immediate contact with the e ips.

To the washed chips there are then added 435 parts ofsulfurous acid solution of 5.5% concentration to form ammonium bisulfite in immediate contact with the chips and the vcook is completed in the usual way save that the temperature can be rapidly raised above 110 0., thus allowing a shorter than usual penetrationperiod and a more rapid cook. It will be found that the resulting pulp is of a white color and of exceptionally high quality, easily bleachable and of high alpha cellulose content. Era-ample %.-Into a digester as described I in Example 1, there are introduced 100 parts by weight of slash ine containing a high i content of heart wood Thereafter 500 arts of ammonium hydroxide of 3% strengt are introduced into the di ester and circulated through the chips for 2 ours at 100 C. The temperature is then allowed to drop to 70 (3., the ammonium hydroxide containing solution drained off, and treated as described in Exam lel and the chips washed with water at 20 for about 15 minutes. The washing water is circulated thoroughly thruout the chips and drained off.

Thereafter 500 parts of ammonium bisulfite li nor of 5.5% total S0 and 1.15% combine O is introduced into. the digester and the cook com leted' in the usual way. The resulting pro net is low in itch content free from shives' and uncooke ggpd color and strength, and easilybleach- E e.'

I claim: 1. A process, for the which comprises subjecting cellulosic material to pre iminary treatment with a dilute portions, oi

production of pulp aqueous solution of ammonia and thereafter digesting with ammonium bisulfite.

whiehcomprises subjectin resinous wood to prelim nary treatment wit a dilute aqueous solution of ammonia and thereafter digesting with ammonium bisulfite.

3 A process for the production of pul which comprises subjecting cellulosic materi to preliminary treatment with a dilute aqueous solution of ammonia, removing said solution of ammonia, and washing with a relatively more dilute aqueous solution of ammoma. p 4. A process for the production of pulp which com rises subjecting cellulosic material to pre iminary treatment with a'dilute aqueous solution of ammonia, removing the greater part of said solution of ammonia, and washing with a relatively more dilute aqueous solution of ammonia.

5..A process for/the production of pulp which comprises subjecting resinous wood to preliminary treatment with a dilute aqueous solution of ammonia, removing said solution of ammonia, and washing with a relatively more dilute aqueous solut1on of ammonia.

6. A process for the production of pulp which comprises subjecting cellulosic material to preliminary treatment with a dilute aqueous solution of ammonia at a temperature in excess of 90 6., and thereafter digesting with an ammonium bisulfite solution.

7. A process for the production of pul which comprises subjecting cellulosic materia .to preliminary treatment with an aqueous solution of ammonia of from 2-.4% strength at a temperature in excess of 90 (3., and

39 thereafter digesting with an ammonium hi sulfite solution. a

8. it. process for th production of pulp which comprises circulating a dilute aqueous solution of ammoniaover wood chi s in the proportion of solution to chips of-a out 5:1

by wei ht, for about minutes, at a temperature o 100-110 0., removing said solution of ammonia without reduction of pressure, circulating about two parts by weight of a to relatively more dilute solution of aqueous ammonia per part of wood chips, for about 15 minutes at 7 0 (3., removing all but about 0.65 parts of said solution, and thereafter cooking with about at parts of sulfurous acid 45 solution of about 5.5% concentration.

ln testimon whereof I it my siaturea R GER W RICDSUN. 

